Deco with too less air, options from the book

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

I wouldn't take what I read in Shadow Divers as anything other than entertainment ... Kurson admittedly took a bit of literary license to make the story flow. Also, he's not a diver ... and anyone who's ever read a newspaper account of a diving accident understands how wrong non-divers can get it, even when they're trying hard to report the facts.

Couple things to consider about using Navy tables ... they were created based on the experiences of very fit 20-something year old men ... who had ready access to an on-board hyperbaric chamber. So I'd be wary of considering Navy tables suitable for use by your typical recreational diver.

And finally, if Bernie Chowdhury chooses to take great risks with his decompression choices, my guess is that he's doing so based on experience and knowledge that most divers on ScubaBoard do not possess. An analogy ... if Jimmie Johnson or Jeff Gordon were to go on the internet and explain how to steer out of a high-speed spin, we'd be all ears. But if someone learning how to drive were to ask the same question of his driving instructor, the correct answer would be to not put yourself into a position where you'd have to do that.

Same applies here ... the "correct" answer really depends on who's asking the question.

... Bob (Grateful Diver)


Not sure how this matters with what was being discussed - go back and read the question about why divers in their position wouldn't go down to try to do an emergency deco with a new tank, then the answers we gave. Even if that part of the story was fictional, the answers supplied fit the hypothetical question.

I'm not even sure your entire post was needed as it's just a re-hash of what has already been said for 12 pages in this thread. Never had a problem with you, Bob, but it seems like you're writing in a condescending manner for no reason.

A good point and theory to contemplate was brought in the thread (finally). You may not be able to handle it nor like it, but a new diver will be able to look it up, study, and eventually choose for himself or herself once they understand what there is to get a grasp of.
 
And finally, if Bernie Chowdhury chooses to take great risks with his decompression choices, my guess is that he's doing so based on experience and knowledge that most divers on ScubaBoard do not possess.

I doubt this, Bob. NOBODY has a lot of experience in blowing off enormous amounts of decompression, because very few people get to do it twice. Reading The Last Dive, it's pretty clear he blew off the deco because he was out of the gas to stay underwater, and he paid a pretty awful price for it.
 
Not sure how this matters with what was being discussed - go back and read the question about why divers in their position wouldn't go down to try to do an emergency deco with a new tank, then the answers we gave. Even if that part of the story was fictional, the answers supplied fit the hypothetical question.

I'm not even sure your entire post was needed as it's just a re-hash of what has already been said for 12 pages in this thread. Never had a problem with you, Bob, but it seems like you're writing in a condescending manner for no reason.

A good point and theory to contemplate was brought in the thread (finally). You may not be able to handle it nor like it, but a new diver will be able to look it up, study, and eventually choose for himself or herself once they understand what there is to get a grasp of.
That "C" word seems to be getting tossed around pretty casually in this thread. I'm not trying to be condescending ... I'm asking you all to consider who reads this board, and to what end they may attempt putting the information they receive here.

My concern is to not encourage someone, through misinformation, to do something that will injure or kill them.

gilldiver:
Assuming you were not using a He mix, You could fall back on to US Navy Air tables which give you a deco of:

3 minutes @ 20 feet
11 minutes @ 10 feet

This was a very standard dive on the USS Bass and we would pad it to:

5 minutes @ 20 feet
15 minutes @ 10 feet

The US Navy tables are not considered to be ideal anymore but houndreads of thousands of dives were done on them with accident rates of less then 1/10% or less.

Pointing out that someone recommending Navy air tables hasn't considered who those tables were written for isn't condescending ... and as someone else noted, the accident rates on those tables were substantially higher than stated.

HowardE:
Also - for those interested... The US Navy tables are based on 100 dives performed by navy divers.... Of those 100 dives... 5 of the dives resulted in DCS. I guess 5% is acceptable?

My reference to the Shadow Divers commentary wasn't in response to why they didn't go back down ... but rather to all the commentary that preceded that question.

I doubt this, Bob. NOBODY has a lot of experience in blowing off enormous amounts of decompression, because very few people get to do it twice. Reading The Last Dive, it's pretty clear he blew off the deco because he was out of the gas to stay underwater, and he paid a pretty awful price for it.

I wasn't referring to blowing off the deco ... I was referring to his solution to the problem.

boulderjohn:
In The Last Dive, author Bernie Chowdhury describes his near-fatal DCS experience while diving deep air solo. Almost certainly under the influence of narcosis, he started up the wrong ascent line off a wreck before realizing he was not on the line on which he had left his deco bottles. Because of a ripping current, he had to crawl to the other end of the wreck to get to the correct line, but he crawled completely around the wreck and found himself back on the wrong line. Now nearly out of air, he surfaced and prayed for a successful chamber experience. He got it.

Reflecting on this experience, he seems to feel the only mistake he made was not using a full-face mask so he could transmit a radio distress message to the surface. I don't recall that he even considers the idea that a buddy might have been helpful.
His choices ... which he made based on his experience. To my concern, better choices would've been ...

a) dive with a buddy, or
b) keep your deco bottles with you, or
c) once you're realized you're on the wrong line, stay there and deco as best you can on your back gas

Asking people to consider making better choices isn't condescending ... at least not to my way of thinking.

Now I'm going to ask a question of my own ... how many of you responding to this thread have actually ever done a planned deco dive? Because the mentality that goes into planning and executing such a dive is rather different than diving within NDL's ... and it's quite possible that what you're seeing as condescencion is nothing more than a difference in perspective based on experiences.

... Bob (Grateful Diver)
 
I'm not seeing condescention.

I have made some planned deco dives. Wreck dives, no penetration. In some situations e.g. cave restrictions, wreck penetrations in tight quarters, I can see that from your list a) might not always be possible.

However, for the kind of diving I'm doing, b) keeping my deco bottles with me makes the most sense, with c) as a backup.

I think the point of Mr Chowdhury's story IIRC was to illustrate the following: his overconfidence after making many deeper dives past 150 ft so that 150 ft seemed shallow to him; making a poor choice by doing a second dive to the wreck when he was feeling tired and congested after a cold and taking medication for that; getting obsessed with recovering a porthole; and that air was a poor choice for his dive.

I thought in context of what he was describing the lesson came through quite clearly.
 
I have not read Last Dive, or Shadow Divers, in a while so I will only talk about both of theses events from memory.

Bernie had a charter on the Seeker to the Northern Pacific, a turtle WWII era wreck roughly 400 feet long. He had both divers and students on the charter with him, and he ran a permanent reel line from the anchor line, to the opposite end of the wreck, to benefit him and his divers with navigation. It was a two day overnighter.

On the dive where he was injured, he and his buddy went from one end of the wreck to the other. As they got back to the anchor line, the buddy ascended as you might expect. Bernie got turned around and continued on the reel line, but now going the other way, to the other end of the wreck. Now at the wrong end of the wreck, and now out of gas, he did what I would describe as a direct ascent to the surface. As you might expect he suffered DCS symptoms almost immediately, with CNS symptoms consisting of a loss of hearing.

Bernie was really a cave diver, using cave techniques on a wreck. Although the two deciplines have some similarities, they are not the same. He relied solely on his line. He did not:

Keep all of his gas with him.

Use a compass. On a Big Iron wreck a compass will not work well, but it works well enough to determine North from South in many instances.

He did not understand the wreck and was not able to identify elements of the wreck like the keel, bilge keel, bow and stern, and use this information to navigate.

He did not mark the ancor line with a strobe light. The light might have helped him to notice the anchor line.

He did not orient himself to the direction of the current, which can help a diver who is confused about which way to go.

Navigation does not happen on wrecks by its own. You need to work at it. As is true with most deep dives, the buddy was not in a position to help. Bernie screwed up, Bernie paid the price.

Cheers

JC
 
Last edited:
Nothing other than entertainment? Cute. I guess you know Rob, and the story, better than I do? Actually, he can't even swim.

The USN tables were developed by the USN and based on 100 test dives by USN divers of varying ages and levels of experience, not 20 year olds. You can see that the USN still uses divers like this for their tests, next time you are at the Experimental Diving Unit in Panama City.

Anyway, on to the Rouses. They entered the wreck through the round hatch opening on the forward Contol Room Bulkhead. This was the access used by the crew. Chrissy went forward to the galley. Chris followed when Chrissy did not return as planned and found him trapped. He extricated him and they exited through the port side breach between the forward Control Room Bulkhead and the pressure hull itself. The opening was about 3 feet across at the time, and probably 5 feet to the port from where they entered. I would suspect that visibility was zero.

Chris Rouse became unresponsive at the back of the boat. Chrissy was unable to use his legs before we even dragged him from the water, and not in a position to give us much in the way of information either. We know how they went into the wreck, where Chrissy was working, what fell on him, and where they exited, because they used a penetration line. Unfortunatley, they tied off the pen line where they entered the wreck, not at the anchor line where they left their gas.

On the next trip to the site, we found and videotaped the 3 stage bottles they could not find, the line going in the hatch, the collapsed wreckage that apparently trapped Chrissy, and the penetraion line still fouled on the life raft Chrissy was trying to remove, and then followed the line out of the wreck. In one way, out another. We gave the video to the Rouse family.

As a footnote, the Rouses had gas. Their tanks were not empty. They also had other divers in the water. They also had hookahs at 20'. Their problem was not that they were out of gas, or options. The problem that they could not overcome was that they were overwhelmed by their circumstances, first getting trapped and then lost. This was incredible stress. At least Chrissy, simply could not stay in the water another minute, and had to surface. The problem they could not overcome was psychological or mental, not physical, and there is an incredibly important lesson to be learned here.

It is not always the nuts and bolts. We have the ability to make the wrong decision for a lot of reasons.

Cheers

JC





I wouldn't take what I read in Shadow Divers as anything other than entertainment ... Kurson admittedly took a bit of literary license to make the story flow. Also, he's not a diver ... and anyone who's ever read a newspaper account of a diving accident understands how wrong non-divers can get it, even when they're trying hard to report the facts.

Couple things to consider about using Navy tables ... they were created based on the experiences of very fit 20-something year old men ... who had ready access to an on-board hyperbaric chamber. So I'd be wary of considering Navy tables suitable for use by your typical recreational diver.

And finally, if Bernie Chowdhury chooses to take great risks with his decompression choices, my guess is that he's doing so based on experience and knowledge that most divers on ScubaBoard do not possess. An analogy ... if Jimmie Johnson or Jeff Gordon were to go on the internet and explain how to steer out of a high-speed spin, we'd be all ears. But if someone learning how to drive were to ask the same question of his driving instructor, the correct answer would be to not put yourself into a position where you'd have to do that.

Same applies here ... the "correct" answer really depends on who's asking the question.

... Bob (Grateful Diver)
 
...
As a footnote, the Rouses had gas. Their tanks were not empty. They also had other divers in the water. They also had hookahs at 20'. Their problem was not that they were out of gas, or options. The problem that they could not overcome was that they were overwhelmed by their circumstances, first getting trapped and then lost. This was incredible stress. At least Chrissy, simply could not stay in the water another minute, and had to surface. The problem they could not overcome was psychological or mental, not physical, and there is an incredibly important lesson to be learned here.

It is not always the nuts and bolts. We have the ability to make the wrong decision for a lot of reasons.

Cheers

JC


Wow, I read that book a while ago and did not get that from the reading it. They both had air and options and couldn't use them.....
 
The statement that the Navy tables are based on only 100 dives with a 5% hit rate is a bit misleading. Millions of dives have been made by the Navy on its tables and there is not a 5% hit rate. They are one of the most used and most documented set of tables out there.

According to Larry Taylor, Diving Safety Coordinator at the University of Michigan, “The US Naval Safety Center report on diving illness and safety (as described in SPUMS, Sept 1997, p. 179) stated that for the period 1990-1995, there were 648,488 logged dives with … 382 reported cases of decompression sickness.” That is more like a 0.06% hit rate.
 
possibly they are trying to compare the incidence of DCI for dives that are taken to the absolute limit of the tables versus all dives which might not be as extreme?
 

Back
Top Bottom